Amazon's revenue came to a slowdown across the board. It's total revenue grew 16.9% compared with the year-ago period, representing the slowest expansion since the first quarter of 2015. Its North American revenue saw a 17% increase, compared with last year's 46% growth, while international growth dropped to just 9%, down from the previous year's 34% growth rate.

Amazon's advertising business, which is looped under the "other" category, significantly slowed down, seeing only 34% revenue growth to $2.7 billion, after growing at least 60% in the past five quarters. Its physical stores revenue, primarily consisting of Whole Foods sales, grew just 1% year over year to $4.3 billion.

Amazon's cloud service, meanwhile, continued its solid growth with a 41% sales increase, although that was also a deceleration from last year's 49% growth rate.

Investors, however, are seeing more profitability from Amazon in exchange. Net income hit a record $3.6 billion, and its operating profit of $4.4 billion represented a 7.4% margin, up from last year's 3.8% margin.

The wider margins come from growth in businesses like cloud, advertising and third-party seller services, where profits are bigger but total sales are smaller. Whole Foods, a slower-growing business, is also now fully integrated into Amazon's results.

But Amazon's operating profit guidance for the second quarter came in the range of $2.6 billion and $3.6 billion, far below the $4.2 billion street estimate, indicating heavier investments going forward. Amazon's CFO Brian Olsavsky said during the call with analysts that part of the lower guidance is due to an $800 million investment in making free one-day delivery shipping the default for Prime members.

Amazon also announced that it now has more than 30 million active users for its Fire TV streaming device. That's more than Roku's 27 million active accounts announced in January.

Amazon has been one of the best-performing big tech stocks this year, up 28% in 2019. It is currently the third most valuable company in the world, behind Microsoft and Apple.